In short: A color contrast checker calculates the WCAG contrast ratio between text and background colors; WCAG 2.2 level AA requires at least 4.5:1 for normal text and 3:1 for large text.
About Color Contrast Checker
Low-contrast text is one of the most common accessibility failures on the web, and it affects everyone reading on a phone in sunlight, not just people with low vision. The Web Content Accessibility Guidelines (WCAG) define a contrast ratio from 1:1 (identical colors) to 21:1 (black on white) and set minimum ratios for text and interface elements.
This checker uses the WCAG 2.x relative-luminance formula. Level AA requires 4.5:1 for normal text and 3:1 for large text (at least 24px, or 18.66px bold) and for UI components such as input borders and icons (success criterion 1.4.11). Level AAA raises text requirements to 7:1 and 4.5:1. See the W3C explanation for details.
How to use Color Contrast Checker
- Enter or pick a text color and a background color (hex, rgb() or CSS color names).
- Read the ratio and the pass/fail table for normal text, large text and UI components.
- Adjust colors until the levels you need pass.
Examples
#767676 on #ffffff is 4.54:1 — the lightest gray that passes AA for normal text.
White on #2563eb is 5.17:1 — passes AA for normal text but not AAA. White on the lighter #2f6bff is 4.49:1 and fails AA, even though it looks almost the same.
Frequently asked questions
What contrast ratio do I need?
For WCAG 2.2 AA: 4.5:1 for body text, 3:1 for large text and for UI components and graphics. AAA: 7:1 and 4.5:1 for text.
Does opacity count?
The ratio is calculated on the final rendered colors. If text is semi-transparent, measure the blended color.
What about WCAG 3 / APCA?
APCA is a proposed method for future guidelines and is not yet a standard. WCAG 2.x ratios remain the legal and contractual benchmark in most places.
Are logos exempt?
Yes. Text that is part of a logo or brand name and purely decorative text have no contrast requirement.
Updated November 2026 · Free, no signup · How we build and test tools